Forum Schedule Spring 2025

In this talk, I will review recent work that allowed us to obtain a better understanding of the neutron star equation of state and neutron star properties by use of multimessenger observations of (binary) neutron stars. I will also discuss recent and current efforts in modeling binary neutron star mergers that will help enable constraints on the unknown finite temperature nuclear equation of state by use of third-generation gravitational wave observatories.

To date, over 5,700 exoplanets have been discovered, with thousands more candidates awaiting confirmation. Thanks to advancements in observational technology, the map of known exoplanets has expanded dramatically, reaching from the solar neighborhood (100-200 parsecs) to distances of up to several thousand parsecs within our Galaxy. This marks the dawn of a new era in the census of exoplanets in the Milky Way. A fundamental question in Galactic exoplanet research is: How do the properties of planetary systems vary across different positions and ages within the Galaxy? Answering this question will offer valuable insights into the formation and evolution of the diverse exoplanet populations found in various Galactic environments. In this presentation, I will discuss our recent work, which focuses on the age-dependence of different planet types (such as hot/warm/cold Jupiters, super-Earths/sub-Neptunes, and ultra-short period planets), leveraging data from surveys like LAMOST, Gaia, and Kepler to uncover evidence of their long-term evolution.

This talk explores the distribution of baryons, metals, and dust in galaxies, as well as the circumgalactic (CGM) and intergalactic (IGM) media, using the CROCODILE cosmological hydrodynamic simulations performed with the GADGET3/4-Osaka code, alongside insights from the AGORA code comparison project. Our simulations incorporate supernova (SN) and active galactic nucleus (AGN) feedback models to investigate how these processes shape chemical enrichment and the baryonic distribution around galaxies. AGN feedback drives metal transport to intermediate scales, while SN feedback predominantly shapes smaller-scale structures, profoundly influencing the CGM and IGM.

We leverage a variety of astrophysical models implemented in CROCODILE to study the interplay between baryonic and metal distributions and their observational tracers, including the Lyman-alpha (Lyα) forest, large-scale IGM tomography, and fast radio burst (FRB) cosmology. These approaches allow us to map HI absorption and ionized electron distributions, offering new insights into the structure of the IGM. Highlights include results from IGM tomography and applications to FRB cosmology.

By connecting simulations of galaxy evolution with these observational strategies, this study deepens our understanding of the CGM and IGM in the early universe. The findings provide valuable guidance for future observational surveys (e.g., Subaru PFS) and contribute to refining theoretical models of galaxy formation and the large-scale distribution of baryons. cf. https://sites.google.com/view/crocodilesimulation/

The last decade has been transformative in better understanding the role and impact of funding low- to mid-Technology Readiness Level strategic astrophysics technologies to mature components, sub-systems, and systems, with the final goal of infusing them into upcoming space missions. After over $220M in investments in technology maturity grants over the past decade, it became imperative to evaluate the effectiveness of these efforts in enabling new instrumentation, payloads, and missions. Space astrophysics in the last two decades has entered a unique set of requirements and constraints. For example, NASA astrophysics addresses the most difficult and profound questions about the nature and origin of the Universe and is seeking life outside our Solar System, however, it is a photon-starved discipline, demanding exquisite performance from all systems and subsystems utilized in on-sky observation and detection. Furthermore, current astrophysical science and technology requirements are exquisite and highly demanding (e.g., search for life, dark matter, dark energy) that makes them enabling for astrophysical research but enhancing for the rest of other sciences and applications. We have also discovered that the obstacles to reach the next level of detection in observational astrophysics are not scientific in nature, but they are technological in nature. These topics will be discussed by providing some examples and future objectives in identifying applications from emerging technologies as applied to astrophysics technology development for the upcoming space missions.

The weakly-interacting neutrinos are produced by nuclear reactions in the sun, by interaction of cosmic rays with earth's atmosphere, and by accelerators and nuclear reactors on earth. A number of experiments have shown that neutrinos oscillate among different flavors and therefore have mass, which opens the door to new physics beyond the standard model of particle physics. Neutrinos also play prominent roles in the early universe and during the evolution and explosion of massive stars. They are unique messengers from extreme astrophysical environments where neutron stars and black holes are born and where high-energy phenomena occur. I will review what we have learned so far about neutrinos and their associated physics and astrophysics, which are connected with a range of Nobel prizes.

Spatially resolved observations of protoplanetary discs have revealed a multitude of substructures. From gaps and cavities, to spiral arms and perturbed kinematics, these observations are highly suggestive of companion-disc interactions from planetary to stellar mass objects. However other mechanisms, such as the gravitational instability (GI) or late-stage infall, may explain some of these structures. Using hydrodynamical simulations and radiative transfer to produce mock observations, we can understand how to distinguish between these scenarios. By directly comparing with observations, I will show how undetected binary companions and late-stage infall may be an important but overlooked source of disc substructures.

The two-mile-long linear accelerator (linac) at the SLAC National Accelerator Laboratory has begun a new phase of its career with the creation of the world’s first X-ray free-electron laser the Linac Coherent Light Source (LCLS). For over 60 years, SLAC's linac has produced high-energy electron beams for cutting-edge physics experiments, leading to the discovery of elementary particles, multiple Nobel prizes and ushering in the golden era of particle physics and the standard model. Now, scientists continue this tradition of discovery by using the linac to drive a new kind of laser, creating X-ray pulses of unprecedented brilliance.

LCLS produces femtosecond (10-15 s or 1 quadrillionth of a second) pulses of X-rays more than a billion times brighter than the most powerful previously existing X-ray sources. These ultrashort X-ray pulses are used much like flashes from a high-speed camera, enabling scientists to take stop-motion images of atoms and molecules in motion. With over 13,000 scientific user visits in its first 10 years of operation, researchers from around the world have conducted groundbreaking experiments in fields as diverse as chemical catalysis, human health, quantum materials science, and the physics of planetary formation. Data from LCLS experiments have generated over 1450 articles in peer-reviewed scientific publications, with a quarter of them appearing in prominent journals like Science and Nature.

In this talk I will present a historical overview of the LCLS and discuss some of the exciting science it is enabling, from serial-femtosecond protein-crystallography to controlling emergent collective behavior in quantum materials. I will also describe the massive upgrade projects currently ongoing at the LCLS including the new superconducting-accelerator-driven LCLS-II and HE.